Telephone system



April 23, 1942- J. w. BRUBAKER 23 L TELEPHONE SYSTEM Filed Feb. 4, 1959 I 2 Sheets-Shegt l INVENTOR J. W BRUBAKER A ril 28, 1942.

J. W. BRUBAKER TELEPHONE SYSTEM 2 Sheets-Sheet 2 Filed Feb. 4. 1959 INVENTOR J. WBRUBAKER WYQ'WiM ATTQRNEV Patented Apr. 28, 1942 ICE TELEPHONE SYSTEM James W. Brubaker, Freeport, N. Y., assignor to Bell Telephone Laboratories, Incorporated, New York, N. Y., a corporation of New York Application February 4, 1939, Serial No. 254,572

7 Claims.

This invention relates to telephone systems and particularly to systems in which coin stations are equipped with designation transmitters for establishing connections automatically.

The objects of the invention are to facilitate the establishment of different types of connections, such as connections to subscribers lines and to Operators positions; to improve the signals that are used to distinguish the type of call that is being made from a coin station; to minimize the acoustic disturbances incident to the deposit of coins; and otherwise to effect improvements in systems of this character.

It has been the practic heretofore to permit the patron of a coin station to dial and establish a connection to a local subscribers line and to deposit his coin after the called party answers. This is known as post-pay service. When the called party responds, the talkingconnection-is disabled at the central oifice, and a tone is sent to the calling party notifying him that he must deposit a coin. The subsequent deposit of the coin reestablishes the connection, and conversation may then proceed. Also it has been possible in these prior systems for thecoin patron to dial for an operator who makes the connection for him and requests him to deposit the necessary coins. In this case the operator verifies the deposit of the coins by means of the coin tones that are transmitted over the line to her headset. It will benoted, therefore, that the act of depositing the coin serves in one case to send a signal to cause the automatic reestablishment of the talking connection and in theother case to send audible signals to the operator.

According to the present invention improvements are secured in these prior systems by means of a circuit arrangement in which the deposit of the coins by the coin patron, and with out any discriminatory act on his part, causes a signal current of reduced intensity to be sent to the central ofiice to effect the automatic reclosure of the talking connection, on a call to a subscribers line, and causes signal current of full intensity to be transmitted to the central oflice, when the coin patron has dialed for the operator, to notify her by the audible signal tones that the necessary coins have been deposited. One of the principal advantages of this feature is that the operator is better able to hear and distinguish the coin tones since they are transmitted over the connection by currents of unreduced intensity.

A further feature and advantage of the invention is that the deposit of the coin for the transmission of the signal tone to the operator does not appreciably alter the intensity of the current normally flowing. over the line to which the operators headset and also the receiver at the coin station are efiectively connected. Consequently the deposit of the coins is not accompanied by acoustic disturbances.

The foregoing and other features of the in'vention will be discussed more fully in the following detailed specification.

In the drawings accompanying the specification Figs. 1 and 2 when taken together disclosean automatic telephone system including the equipment essential to an understanding of the present invention. I

Fig. 1 illustrates, largely in diagrammatic manner, a line finder switch and the associated first selector switch. This figure also discloses the details of the coin-control circuit interconnecting the line finder and first selector. The figure fur ther discloses a telephone line equipped with a coin-controlled substation. I

Fig. 2 illustrates diagrammatically a succeeding selector switch and a connector switch for completing connections to a calledsubscribers line. This figure also illustrates an operators position and a trunk circuit extending to her posi tion from the first selector switch of Fig, 1.

The equipment at the substation of the coin line I00 includes the usual telephone transmitter I0l, receiver I02 and an impulse dial I03. It also includes a coin receiving chute I04, a tone gong I05, and contacts I06 which are opened momentarily by the. action of the coin falling through the chute I04 and into the till below. In parallel with the contacts I06 is'a. resistance I01, which in turn is shunted by; a rectifying element I08. I 1

The purpose of the "resistance I 0T is to diminish the flow of current over the line to the central office to cause the release ofa relay thereat to condition for conversation a connection that has been established to a subscribe-rs line. As will be explained more fully hereinafter, the direction of current flowing over the coin line I00, on a call extended to a subscribers line by dialing, is such that the rectifier I08 does notinterfere with the function of the resistance I01, whereas on a call to an operators position current flows in the opposite direction over the coin line I00 and passes through the rectifier I08 undiminished by the resistance I01 when the contacts I06 are momentarily opened by the deposited coin. In this latter case the operator is listening to the tone produced by the gong I05,

established, serves to transmit a signal of reduced" intensity to operate equipment at the central office for the purpose of rendering the established connection efiective forconversation; and

, the same act of depositing a coin at the request of the operator on a call to her position serves to transmit to the operatorasignal tone of unreduced intensity.

The coin line I00 appears in the bank of a line finder switch F. at the central office, and the finder F'is interconnected by a coin-controlled circuit C'Cwith the first selector switch S. The. selector S hasaccess to succeeding switches, such as selector 'S-I .and connector 0, to other lines in thesexchange. The. selector S also has access by way of the trunk circuit T to. an operators position.

'While the invention is not limited to any particular type of telephone. system; it may be assumed forv the purpose of the present disclosure that .the central oflice illustrated is equipped with switches of the well-known 1 step-by-step type. And the rectifying element used at the substation in conjunction with the resistance and coinoperated contacts may be. of any suitable type, such as. the copper-:oxiderectifier.

The invention will be explained further by describing the operation of the equipment shown in the drawings. To this end it will be assumed first that a patron at the substation of the coin line I00 wishes to conversewith the subscriber of line 200. The calling patron first removes the receiver ,I 02 from the, switchhook, closing. the line loop. circuit to initiate the hunting operation of the line finderF. When the finder F seizesthe callingline a dialing circuit is completed through to the first selector switches. This circuitmay be traced from battery through theleft winding of impulse relay I09,'normal contact of relay IIO, I

contacts of relay l I0. through the right winding of relay I09 to ground. Relay I09 operates and causes the operation oflthe slow-release relay II9, which appliesholding groundpotential to the sleeve conductor I to hold the line finder switch I in, the well-known manner.

. Since the coin; line I00 is a-post-pay line, the patron proceeds to dial the desired number without depositing a coin. The operation of the dial mil-transmits the-usual series of designation impulses, and the selector switches S and S'I are operated successively to extend the line'to -the connector-switch C. When connector C i seized,

the-"impulse circuit is extended. through to the;

windings vof the.- mpulse relay Y 20 I. by way of the;

front contacts of the operated cut-through relay H0 in selector S, and a similar relay in selector SI, and the normal contacts of relay 202 associated with the connector switch C. The calling patron, continuing to dial, sets the connector switch C on the terminals of the called line 200, the called subscribers lineis rung, and, when the called party answers, relay, 202 operates in series with his line. to reverse the connection of the windings of relay 20I to the circuit incoming from the calling station.

Up to the time the called party answers, the directioncf current flowing through the windings of polarized relay III is such that the relay does not operate. However, the reversal of 0111".- rent, caused'by theanswering of the called line, results in the operation of relay I II and the closure of its contacts Relay III in operating causes the operation of relay I2I in a circuit traceable from battery through the normal contacts of relayI 22, contacts'of relay. I I I, conductor I23 throughthe normal contacts of relay II3, windings of relay I2I vtoground; Relay I2I closes an obviousgcircuit forthe operation of relay IM and also closes a circuit through the upper normal'contactsof relay H3 and the winding of relay I25 tobattery. Although relay I25 is marginal, it receives sufi'icient current from this circuit to operate. circuit from battery on conductor I23 through the lowercontact of relay; I24- and. the winding of relay II3 to ground, Relay II3 operates and looks through its inner lower. front contact inde-,

pendently of its operating. circuit.

Relay II3 in operating opens the tip and ring conductorsof the established connection to dis ablesaid connection so that conversation cannot ensueuntil the calling patron has deposited a coin at the substation. During the time the connection issevered. at the contacts of relay II3 the switches beyond are held by a bridge circuit closed through the middle front contactsof relay I24 and the resistance I29. Relay II3 also connects relaysI2I and I25, to the conductors of the coin line I00 for the purpose of testing the line and detectingthedepositing of the necessary coin. The test circuit may be traced from. battery through the winding of. the marginal test relay- I25; upper front contacts of relay H3 thence through the line finder and over conductor II'I, through the switchhook contacts at thersubstation, through the parallel paths including coin contacts I06 andresistance I01 to conductor IIB, thence as previously: traced over the other line conductor through the finder'and the lower front contacts. of relay H3, windings of 'relay I2I to ground. Since the contacts I06 close a short circuit around resistance I01, the intensity of current fiowing-inthe test circuit is sufilcient to hold the marginal relay I25 operated. It will be noted that the polarity of the recifier I08 i such as to oppose. the flow of current in the test circuit above traced. Accordingly, the current in this test circuitmust flow by Way of the contacts I00. when closed, or by way of the resistance I0! when the contacts. are open.v

The calling patron, having completed his dialing and. having. established agconnection to the called subscribers line, is apprised by means of a signal tone that the connection will be ready for conversation assoon as he deposits the necessary coin. The tone, circuit may be traced fromthe tone source I26 through. condenser I21, closed contacts of relay. II3, through the. windings 011' relay iiI'ZJ' and...a1so.over the test circuit Relay I24 in operating closes a.

above traced through the winding of induction coil I I5 atthe substation and returning over the line through the winding of test relay I25. The patron hears the distinctive. tone in his receiver I02 and depositsa coin I28 in the chute I04. As the coin falls, it hits the gong I05, serving no useful purpose on this type of call, and an instant later opens the coin contacts I06 for a brief interval. The opening of these contacts includes the, resistance I01 directly in the test circuit, diminishing the intensity of the current flow and; causing the marginal relay I25 to release. Relay I2I, however, being sensitive, does not release at this time. Relay I25 completes a circuit from battery through the inner upper contact of relay II3, closed contacts of relay I25, uppermost closed contacts of relay I24, through the winding of relay I22 to the grounded sleeve conductor I20. Relay I22 operates and locks through its closed contacts to the sleeve conductor I20. In operating, relay I22 removes battery from the conductor I23 causing relay H3 to release. Relay II3 disconnects the relays I2I and I25 and recloses the tip and ring conductors to condition the established connection for conversation. Relay I2I in releasing opens the circuit of relay I24. Relay I22 remains energized to prevent the reoperation of the associated relays during the conversational period. The release of relay I24 opens the bridge circuit through the resistance I29 and restores the control of the switches to the switchhook contacts at the calling station.

After the coin passes into the till, the contacts I reclose the short circuit around the resistance I01 and the rectifying element I08 to effectively remove these devices from the transmission circuit.

At the end of conversation the calling and called parties replace their receivers, and the established connection is released in the usual manner.

Assume next that the patron of the coin line I00 wishes to call one of the service operators, such as the toll operator. He initiates the call in the same manner, and the line finder F seizes the line and extends it to the first selector switch S. The patron dials the necessary designation to operate the selector switch S to seize the terminals of the trunk T extending to the operators position. As explained hereinbefore, the direction of current flowing through the windings of relayI00 over the calling line, while the selector switch S is being operated, is such that the pol-arizedrelay III fails to operate. When the selector S seizes the trunk T, relay IIO operates to extend the subscribers line through to the trunk, and current is supplied to said line through the windings of relay 203 without change of direction. That is to say, since the patron is calling the operator the established connection should not be disabled, as it was in the case of a call to a subscribers line. Accordingly, no change is effected in the direction of current flow when the selector S seizes the trunk T, and the polarized relay III remains unopera-ted, andrelay II3 does. not operate as before todisable the extended connection. Relay 203 in the trunk closes an obvious circuit for relay 204, and the latter relay operates the slow-release relay 205. Relay 205 applies holding ground potential to the sleeve conductor 206 of the trunk.

A signal (not shown) is displayed in any wellknown manner to attract the attention of the operator. When she responds byconnecting the plug or her cord circuit 201 in the jack 208, the relay 209 operates and closes an obvious circuit for relay 2 I 0. Relay 2 I 0 closes an alternate operating circuit for the relay 205. The operator converses with the calling patron and proceeds to assist him in the establishment of the desired connection. I

Having control of the desired connection, the operator requests the calling patron to deposit the necessary coins in the chute I04 before permitting the parties to converse. As hereinbefore described, the deposited coin I28 first strikes the gong I05 and then opens the contacts I06. At this time current is flowing over the extended connection from the windings of relay 203 in such a direction that it passes readily through the rectifier I08 at the substation. The opening of contacts I06, therefore, is without effect on this call, since the rectifier I08 offers a low resistance to the flow of current and prevents the resistance element I01 from diminishing the current intensity. Thus the tone transmitting current flowing over the connection to the operators telephone continues with undiminished intensity without regard to the action of the coin in opening the contacts I06. Furthermore, since the opening of these contacts does not produce a sudden change in the resistance of the circuit, the objectionable acoustic disturbance that would otherwise occur is obviated.

At the end of conversation the calling patron replaces his receiver on the switchhook, resulting in the release of relays 203 and 204. Relay 204 opens one of the circuits for relay 205, but the latter relay remains operated until the operator removes the cord circuit from the trunk. When she does this, having received a signal that the calling party has replaced his receiver, relays 209 and M0 release, and relay 205 releases to remove holding ground from conductor 206. This permits the release of selector switch S and finder switch F.

What is claimed is:

1. In a telephone system, a line equipped with coin-receiving mechanism at the substation, a central ofiice having automatic switches therein, a subscribers line, an operators position, means controlled by the party at said coin substation for selectively operating said automatic switches to establish either a connection to said subscribers line or a connection to said operators position, means for supplying current to said coin line, impedance means, means responsive to the deposit of a coin in said receiving mechanism when a connection has been extended to the subscribers line for rendering said impedance means effective to change the intensity of the current flowing in said line to transmit a distinctive signal to the central oflice, means at the central ofliceresponsive to said distinctive signal, and means responsive to the deposit of a coin in said mechanism when a connection has been extended to said operators position for sending a distinctive signal to the operator without rendering said impedance means effective.

2. In a telephone system, a coin line having mechanism at the substation for the reception of coins, subscribers lines, an operators position, automatic switches for extending a connection to a subscribers line and for extending a connection to said operators position, means controlled by the party at the coin substation for selectively operating said automatic switches, means for supplying current tosaid coin line, a resistance element at said coin substation, means responsive to the deposit of a coin when a connection has beenex'tended to asubscribers line for effectively including said resistance element in cirsuit to lower the intensity of the current flowing' in the coin line: and to transmit thereby a distinctive signal'over the extended connection, means at the central oflice responsive to said distinctive signal, means responsive to the deposit of a coin when connection has been extended to the operators position for sending a distinctive signal over the coin line to the operator, and means effective While said signal is being transmitted to the operator for disabling said resistance element.

3. In a telephone system, a line equipped with coin-receiving mechanism at the substation, a central office having automatic switches therein, a subscribers line, an operators position, means controlled by the party at said coin substation for operating said automatic switches to establish either a connection to said subscribers line or a connection to said operators position, means for supplying current over said coin line, means effective upon the answering of the called subscriber when a connection is extended to said subscribersline for disabling the extended connection to prevent conversation, a resistance element and a set of contacts rendered'efiective by the deposit of a coin at the coin station for reducing the intensity of the current flowing in the line to enable said established connection for conversation, means responsive to the deposit of a coin when a connection has been ex tended to the operators position for sending a distinctive signal over the calling line to the operator, and means cooperating with said resistance element and said contacts to render said resistance element inefiective when said signal is transmitted to the operator.

4. In a telephone system, a coin line having coin-receiving mechanism at the substation, a subscribers line, an operators position, means for establishing a connection from said coin line either to thesubscribers line or to the operators position, means for causing current to flow over the coin line in one direction'after a connection has been established" to the" subscribers line and in the opposite directionafter a connect-ion has been established to the operators position, a resistance element at" the coin substation, means responsive to'the deposit of a coin for including said resistance element effectively in circuit with said coin line, a rectifying device at said coin substation for forcing the current in the coin line to fiow'through' said'resistance element on a call to saidsubscribers line to transmit" a distinctive signal over the-established connection and for shunting the current around said resistanceelement on a call to the operator to prevent said-resistance element from-efiecting a reduction in the current flowing in said line, meansat the central oflice responsive to said distinctive' signal, and means for sending a dis-- tinctive signal to the operator when said resistance element is in circuit with said coin line.

5. In a telephone system, a, coin line having coin receiving mechanism at the substation, a subscribers line, an operators position, means forestablishinga connection from said coin line eitherto-the subscribers line or to the operators position, means for causing current to flow over the coinnlinein one-direction after a connection has been established to said subscribers line and iinlthe zoppositeldirection after a connection hasbeen established' to the operatorsposition, a resistance element connected in series with said coin line at the substation, normally closed contacts in parallel with said' resistance element opened by the deposit of a coin to include said resistance element efiectively in circuit with said coin line, a-rectifier connected in permanent parallel relation to said resistance element and said contacts, said rectifier serving to force the current in the coin line through said resistance element to transmit a distinctive signal over the established connection on a call to said subscribers line and serving to shunt said resistance element on a call to the operator to prevent the resistance element from effecting a reduction in the current flowing when said resistance element is in circuit, means at the central office responsive to said distinctive signal, and means for transmitting a distinctive tone signal current over the coin line to the operator while said resistance element is in circuit with the coin line.

6. In a telephone system, a coin line, a substation for said line including a coin chute, a gong arranged to be struck by coins passing through said chute, a microphone disposed in acoustic relation with said gong, a subscribers line, an'operators position, means for establishing a connection from said coin line either to the subscribers line or to the operators position, means for causing current to flow over the coin line in one direction after a connection has been established to a subscribers line and in the opposite direction after a connection has been established to the operators position, a resistance element connected in series with said coin line at the substation, normally closed contacts in parallel with said resistance element opened by a coin passing through said chute after the coin has struck said gong, said contacts when opened serving to include said'resistance element effectively in circuit with said coin line, a rectifier connected in permanent parallel relation to said resistance element and said contacts, said rectifier serving to'iorce the current in the coin line through said resistance element to transmit a distinctive signal over the established connection on a call to said subscribers line and serving to shunt said resistance element on a call to theoperator to prevent the resistance element from effecting a reduction in the current flowing when said resistance element isin circuit, means at the central ofiice responsive to said distinctive signal, and means including said gong and said microphonefor transmitting a distinctive tone signal current over the coin line to the operator while said resistance element is, in circuit with the coin line.

'7. In a telephone system, a coin line, a substation for said line including a coin receptacle,

a signal device arranged to be operated by coins passing into said receptacle, acoustic means associated-with said signal device, means for extending said coin line to establish either of two telephone connections of different character,

' means for causing-current to flow over the coin line in one direction when one of said telephone connections has been established and in the opposite direction when the other of said telephone connections has been established, an impedanceelement connected in series with said coin line at the substation, normally closed contacts in parallel with said impedance element opened by the coin passing into said receptacle after the coin has operated said signal device; said contacts when'openedserving toinclude said impedance element efiectively in circuit with said coin line, a unidirectional device connected in parallel relation to said impedance element and said contacts, said unidirectional device serving to force the current in the coin line through said impedance element to transmit a distinctive signal when one of said telephone connections is established and serving to shunt said impedance element when the other of said telephone connections is established to prevent the im- 10 pedance element from effecting a reduction in the current flowing when said impedance element is in circuit, means responsive to the distinctive signal caused by the flow of current through said impedance element, and means including said signal device and said acoustic means for transmitting a distinctive signal current over the coin line while said impedance element is in circuit with the coin line.

JAMES W. BRUBAKER. 

